I did a lesson with my 4th graders at the end of the year last year. They
did it first in drawing media, then as clay relief.

They had to do 2 realistic self-portraits. One had to be in pencil, the
other in which ever drawing media they chose (colored pencil, marker, oil
crayon, regular crayon, etc.) Then they had to cut both of them up and
assemble one portrait. Not reinventing the wheel, but once the got over the
HORROR!!! of cutting up their portraits, the result was really amazing.
Then they did abstract portraits in clay. Kind of fun for the end of the
year.

Also, my 4th graders studied Escher this year and they did fantasy landscape
prints using cardboard to make printing plates. We have a little printing
press, so after they made their printing plate they got to make their prints
using the printing press. They came out quite nice. We just used scrap
cardboard to imitate a woodcut printing plate. (Yes they did understand the
difference between "substractive" and "additive". OH well you work with what
you have!) We also went to our local museum where they had a pretty ok Escher
exhibition. So they really made the connection between their work and
Escher's.